electric cooling fans run too much

Hello I need help with a 2002 chevy engine 8.1 50,000 miles the cooling fans run all the time the ignition. is on used a scan tool and it read the engine temp 45 degress and I feel that is correct This is feed to a ect sensor I think it is ok one reads to dash that is ok the other my scaner picked up is ok I pulled the relay and for the fan ( only one) and the a/c is off...I pulled that the a/c relay too... pulled the plugs out of the pcm and they look ok now. Also at the relay I have one hot wire from each fuse and the other goes to the pcm for a ground cct. ( fourth wire goes to the fan) does that mean the pcm is sending out a ground which runs the fan it is 45 degrees out there no need for the fan now what is next worked on this for four days now checking wiring bad wires nothing yet please I need help nitronorm

IF both fans are on replace the ECT and check the connector to it.

IMO buy new ect temp sensor do not install. connect the connector to the new sensor then start engine see if the fans run or not.. if they don't run then change out the engine mounted sender..

also if that ect circuit is open both fans will run .so if it runs with the new sensor you have and open circuit .

open circuit is -45deg F

j cAT thanks for the reply, yes you are right the open cct is -39 degress when I disconnect the ect sensor connector. The new ect sensor is on it's way here I was hoping that there is something wrong with the old one even though I get a desect reading on the scan tool reads correct temp,, if I run the engine for a while it does change to a good temp.. another funny thing though is the data my scanner will not read live data only ing. turned on and the scanner will work on other cars all live data running down the road any ideas will be greatly appriciated Norm

j cAT thanks for the reply, yes you are right the open cct is -39 degress when I disconnect the ect sensor connector. The new ect sensor is on it's way here I was hoping that there is something wrong with the old one even though I get a desect reading on the scan tool reads correct temp,, if I run the engine for a while it does change to a good temp.. another funny thing though is the data my scanner will not read live data only ing. turned on and the scanner will work on other cars all live data running down the road any ideas will be greatly appreciated Norm

I have the actron CP9680 it does read and show charting of the sensors . like rpm/O2/maf/engine temp /fuel trims. works great on my 1996 /2000 gm vehicles .

having that ability is great to see how the sensors are reporting engine operation.

rust belt vehicles do have electrical issues with this type sensor.

Hello one and all I have a question. I can't get my head around regarding the A/C wiring the circuit shows the high pressure switch as normally closed opens at 430 / 20 lbs closed at 200 / 50 lbs this completes the circuit to ground. Also the a/c refrigerant switch normally open cut out at 2-9 lbs and cut in 22-32 lbs So when the a/c is turned on, where will the high pressure switch be in or out I think closed?? will removing the connector take this out of the cct to remove completion to ground?? or should the wires at the connector be jumpered??? still working on the cooling fans running when the engine is running the temp is 45 degress F outside I don't think we need a/c I would like to stop the fans from running without just pulling the AUX FAN relay I need to be sure the 8.1 engine is getting the proper fuel mjx and that the ECT sensor is not screwing things up thanks for the read Later Norm

the high pressure cutout switch should never open work unless someone over charged the system. that switch disables the AC clutch .

the LOW pressure switch works most all the time esp when the temps drop or the system has a low charge.

when the ac is turned on the primary fan will come on [2 fan system] .. when the pressure gets too high I think around 250 PSI .both fans come on .

ac off engine normal temp the fan should not be on ..

Well I been working on this A/C cct. am I correct the low cct switch needs a mim pres of 60 lbs to close the cct to allow the compressor to run.... and the High pres switch is closed and if the compressor put out too much pressure it opens the circuit to save the day still looking as to why the cooling fans run with engine running thanks for your input Norm

HELLO ALL JUST A UPDATE WITH THE A/C OFF, DEFROSTER OFF, AND THE ECT DISCONNECTED THE ELECTRIC FANS BOTH RUN THE RELAY HAS TWO FEEDS ONE FROM TWO DIFFERENT FUSED THE OTHER TWO PINS ONE TO FAN AND THE OTHER TO THE PCM ARE BOTH GROUNDS SOO LOOKS LIKE THE PCM IS TURNING THE FANS ON OUTSIDE TEMP IS 40 DEGRESS f AND ENGINE IS COLD NORM

Hello I have a Innova scan tool 3130 it has a live data feature works on all cars except the 2002 Chevy 8.1 at this time it will only read the L.D. with the ignition turned on and if I start the engine and hit L.D. it shows lost connection what up with this any ideas thanks Norm:runaround:

the low pressure switch will open shutdown ac when the pressure drops to less than 10 psi . the removal of the ect connector will cause both fans to come on as will an open circuit . PCM senses defect goes into max cool mode.

Thanks so much j cAT I thank you the new etc sensor is due to arrive in the next few days and I was thinking that, it is not the problem. I did get a reading of the engine which I believe to be true from the scan tool on live data with the ignition turned on.. Well j cAT will install and find out if the etc was the problem as I checked a lot of the wiring for any grounds or breaks pins at the pcm etc thanks again Norm

Hello I hope j cAT is near by I need your help again..Today the gm OME part arrived the etc and I did as you suggested I hooked it up and used a ground jumper for the dash gauge..I was keeping my fingers crossed.... started the beast and the fans still ran The plug on the low pres switch with blue and black wires very hard to get to..what a place then I disconnected it and low and behold the fans stopped running after a few seconds...I ran the engine till it got hot Had to keep turning the engine off to get a temp read with the scanner ( ingnition on and live data) it did get to 228 the fans ran for 30 seconds shut off the temp was 194... now have to find out way the low switch has a short to ground or something I have a brand new sensor for sale now later and thanks so much Norm

..I did find something with the a/c off and no defrost if I pull the connector for the low pressure switch black wire ( ground) and a light blue wire (power when engine is running). The fans stop running...I ran the engine till it was 228 degrees according to the scan tool then the fans kicked in and stopped at about 195 degrees Now the scan tool that works on other cars a Innova 3130 with live data will not read
with the engine running any ideas thanks Norm

..I did find something with the a/c off and no defrost if I pull the connector for the low pressure switch black wire ( ground) and a light blue wire (power when engine is running). The fans stop running...I ran the engine till it was 228 degrees according to the scan tool then the fans kicked in and stopped at about 195 degrees Now the scan tool that works on other cars a Innova 3130 with live data will not read
with the engine running any ideas thanks Norm

it does seem like you have a wiring problem . these are difficult to help from internet.

scan tools should work could be a connector issue on the OBD II port. or the tool.